This relates generally to wireless communications circuitry, and more particularly, to electronic devices having wireless communications circuitry.
Electronic devices are often provided with wireless communications capabilities. For example, handheld electronic devices may use cellular telephone communications standards to communicate with cellular networks. Handheld electronic devices typically have a limited battery capacity that is used for performing wireless communications. Unless care is taken to consume power wisely, an electronic device may unacceptably consume a significant portion of the limited battery capacity.
Electronic devices with wireless communications capabilities typically include amplifying circuits that are used to amplify radio-frequency signals prior to wireless transmission. For example, a radio-frequency power amplifier may receive input signals having an input power level and generate corresponding output signals having an output power level. The radio-frequency power amplifier receives a power supply voltage that powers the radio-frequency amplifier.
The power supply voltage provided to the radio-frequency power amplifier can be continuously adjusted based on the magnitude of the transmit signals that are amplified by the power amplifier in a process sometimes referred to as envelope tracking. When performing envelope tracking, overall power consumption is reduced in the device while providing radio-frequency signals over an antenna transmitter path to an antenna. However, when transmitting signals, a significant portion of the signals can be reflected by the antenna back onto the antenna transmitter path, thereby decreasing the stability of the amplifying circuits and consequently generating receiver channel noise and/or causing Adjacent Channel Leakage Ratio (ACLR) degradation. It would therefore be desirable to be able to provide wireless communications circuitry having improved envelope tracking capabilities.